PROJECT 5: Nanotechnology-Based Environmental Sensing. Remediation of highly contaminated Superfund sites requires monitoring and evaluation of the contaminants themselves and their byproducts. Superfund sites have diverse and complex toxic species that contaminate soils, water and the surrounding air;determining what is there, and then determining the extent and effectiveness of remediation continue to present challenges. The rapid development of nanotechnology has offered significant opportunities to produce new sensors for the characterization and monitoring needs of Superfund, not only in the gas phase, but in the different environments where toxic and/or hazardous materials are produced or where they accumulate. We will take advantage of the unique properties of nanoscale materials to detect and measure species such as heavy metals. We plan to develop a collection of sensing protocols for the detection of arsenic, mercury and flame retardant compounds with high sensitivity and specificity. We will develop and apply small-molecule chemical indicators for fluorescence detection of mercury, lead, cadmium, and other toxic heavy metals in environmental laboratory and field samples, with specific interest in seafood and soil specimens. Parallel with this effort, plasmon absorption spectroscopy based on metal nanocrystals will be used for low-cost, rapid detection of mercury in air and aqueous environmental samples. We will continue to develop silver nanocrystal based substrates for ultra-sensitive arsenic detection using surface enhanced Raman spectroscopy. We will extend this sensing platform towards detecting chemical fingerprint for the analytes, distinguishing between the two most common oxidation states of arsenic: arsenate (As^) and arsenite (As'") both in ground water and some other complex media. Similariy this sensing scheme will be applied towards detection of methylated arsenic species with high sensitivity using small sample volume. In addition, we will also develop a sensitive and selective miniaturized electronic sensor for environmental toxicants molecules such as polybrominated diphenylethers (PBDE) using specific molecular recognition elements. These studies should provide new methods to detect and measure chemical and biological species at Superfund sites. The new methods will also be useful for assessing remediation efforts and the reduction of hazardous species at known sources.